Thinking Mathematically (6th Edition)

Published by Pearson
ISBN 10: 0321867327
ISBN 13: 978-0-32186-732-2

Chapter 2 - Set Theory - 2.2 Subsets - Exercise Set 2.2 - Page 68: 67


The total number of proper subsets is $7$.

Work Step by Step

Represented with the roster method, the set looks like this: $\{3, 4, 5\}$ A set of $n$ elements has $2^n$ subsets. This set has 3 elements; therefore, it has $2^3=8$ subsets. However, we are asked for distinct subsets, so we have to take 1 from the result, as one of the subsets is going to be the set itself. The total number of proper subsets is $8-1=7$.
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